The present invention relates generally to a method for drilling and, more particularly, the present invention relates to an improved method for drilling one or more lateral wells.
My previous U.S. Patent Application cited hereinabove discloses how to provide a reliably sealed junction with a lateral well wherein one preferred embodiment utilizes an under-reamed section of borehole. In some cases, it may be desirable to limit the diameter of the under-reamed section for reasons discussed hereinafter. The present application describes how a smaller diameter under-reamed section can be used and still provide, if desired, a lateral wellbore having a diameter substantially the same as the primary well.
Drilling multilateral or horizontal wells from an initial wellbore has become an increasingly popular method for enhancing production and recovery of oil and gas from wellbores. In many cases, the use of multilateral wells has dramatically increased the profitability of oil and gas wells as compared to that of conventional wells. As a result of an increased return on investment, the drilling of multilateral wells has become and is projected to further develop into an important aspect of well enhancement. Moreover, the drilling of multilateral wells has significantly increased the efficiency of oil and gas recovery operations. Multilateral well techniques have been found to be especially effective in areas where the pay-zone or oil/gas deposit may be thin or hard to reach with standard downhole drilling operations.
One primary advantage for drilling multilateral wells involves cost reductions obtained by utilizing a previously drilled wellbore. In drilling multilateral wells, a driller can dramatically reduce the cost of drilling a new well by beginning the new drilling operations at a convenient kickoff depth in a previously existing well. Therefore, many of the modern methods that have been developed for drilling lateral wells make use of an existing wellbore to eliminate the additional cost of drilling the wellbore from the surface.
The technique of drilling multilateral wells has typically consisted of laterally drilling from a previously drilled borehole, sometimes referred to as the primary borehole. It should be noted that the previously drilled borehole is typically cased and cemented, but methods exist in the art for open hole operations, i.e., wellbores or wellbore sections which are not cased or cemented.
However, prior art methods of drilling lateral boreholes suffer from a common significant problem of providing a good seal at the junction between the primary wellbore and the lateral wellbore and/or reliably maintaining this sealed junction over time. If there is a poor seal at this junction, then leakage may occur between the primary borehole and one or more of the lateral boreholes. Leakage at the junction may prevent the possibility of good zone isolation. Zone isolation is an important aspect in the success of many oil and gas recovery operations and may also be required by governmental regulations either now or in the future. Thus, the lack of a reliable seal at this junction is a significant potential problem for multilateral well operations.
My prior application, as identified hereinbefore, discloses in one embodiment use of an under-reamed section of primary borehole which may have a diameter larger than three times the diameter of the primary borehole. However, under-reaming may be problematic in some cases, especially as the size diameter of the under-reamed section increases. For instance, greater torque on the hole opening string is required for larger diameter under-reaming. The larger torque required may lead to more mechanical failures. As well, larger amounts of earth have to be removed from the borehole. Another problem relates to subsequent operations. Depending on the well program, wellbore strings inserted after the under-reaming or hole opening, especially in deviated wells, may tend to be more difficult to guide past the under-reamed section. Thus, the larger the diameter of under-reaming or hole opening, the more likely it is that problems may arise due to the under-reaming or hole opening. Thus, the present invention teaches a drilling method using a reduced diameter under-reamer or hole opener.
A common example of the prior art drilling methods is embodied in U.S. Pat. No. 5,458,209 to Hayes et al. (the ""209 patent). The ""209 patent discloses a method and system for drilling a lateral well with respect to a primary well which is cased. The method discloses positioning a guide means defined as comprising three main parts; a lower end, a central part with an angled ramp and an upper end, and drilling out the casing along the guide at a preselected location. This method may be used to effectively drill multilateral wells, but does not insure a sealed junction.
Accordingly, it would be desirable to somehow provide a method and/or device for drilling one or more lateral wells and establishing a sealed junction between the lateral well and the primary wellbore.
U.S. Pat. No. 5,564,503 to Longbottom et al (the ""503 patent) discloses a method of drilling a lateral well encompassing the steps of setting a diverter within a wellbore, boring through the sidewall of the wellbore at a desired location, lining the lateral well, and cementing the periphery of the junction around the lateral well to obtain a pressure bearing seal around the wellbore. One difficulty encountered when cementing using conventional techniques is that of ensuring a homogeneous flow of cement at the periphery of the junction because of the presence of tubulars and the limited space between the tubulars and the formation about the junction. Another common difficulty is ensuring a uniform fill of the cement about the junction without leaving spaces or voids because of the irregular shape of the interstices about the junction. Accordingly, this method does not necessarily provide a homogeneous cement bond around a lateral well. Another difficulty encountered with the method disclosed in the ""503 patent is the practical impossibility of the using the method to warranty the seal of the junction with the passage of time. Moreover, the amount of cement that actually provides a seal is limited to the cement that actually fills the interstices around the junction between the casing and the formation. Accordingly, pockets filled with mud may prevent the flow of cement into those pockets and therefore could result in structural weakness of the junction. As well, the dirt and debris from the formation can easily mix with and contaminate the cement as it fills the interstices so that the cement is less effective for sealing purposes.
U.S. Patent No. 5,795,924 to Chatterji et al. (the ""924 patent), U.S. Pat. No. 5,820,670 to Chatterji et al. (the ""670 patent) and 6,006,835 to Onan et al (the ""835 patent), which are hereby incorporated herein by reference, disclose use of more elastic materials such as epoxy resin materials or a cement slushy that may be used to provide resilient cement compositions. The cement compositions have improved mechanical properties including elasticity and ductility and may, for instance, be basically comprised of cementitious material, an aqueous rubber latex and a latex stabilizer. Unfortunately, these cements do not necessarily overcome the problems discussed earlier related to pockets, difficult to reach interstices around the junction, and contamination or mixture of such materials by downhole chemicals which may include a wide variety of contaminants. Merely pumping such cements at higher pressures or velocities will not necessarily result in displacing existing fluids or reaching all pockets around the junction. Moreover, high pump pressures and flow velocities may actually increase contamination or mixture problems.
As well, prior art methods for drilling multilateral wells have often required that the lateral well be of a smaller diameter than the primary wellbore. This reduction in size can severely limit further operations in the lateral well. Additional patents related to the aforesaid prior art and attempts to solve related problems include the following:
U.S. Pat. No. 5,945,387, issued Aug. 31, 1999, to Chatterji et al., discloses polymeric well completion and remedial compositions which form highly pliable and durable impermeable masses of desired rigidity and methods of using the compositions. The compositions are basically comprised of water, a water-soluble polymerizable monomer, a polymerization initiator and an oxygen scavenging agent. The compositions are usually foamed and can contain a gelling agent and a solid filler material to increase the density and/or rigidity of the impermeable mass formed and/or a vulcanizable rubber latex, vulcanizing agent and vulcanizing activator to provide durability and other properties.
U.S. Pat. No. 5,992,524, issued Nov. 30, 1999, to Stephen A. Graham, discloses a method and apparatus for flow control in a wellbore in a well having at least one deviated wellbore drilled as an extension of the primary wellbore. More specifically, an assembly is run into the primary wellbore, aligned and anchored and a retrievable or replaceable flow control device is installed within the assembly.
U.S. Pat. No. 6,047,774, issued Apr. 11, 2000, to David W. Allen, discloses the reduced time required for establishing a multilateral well by enlarging a section of a wellbore and running a multilateral tool into the enlarged wellbore section. The multilateral tool, which is suitable for running into a wellbore on a primary casing string, includes a preassembled combination of casing sections that are used to form dual casings strings extending from the primary casing. The multilateral tool incorporates three casing sections, which maintain the diameter of the primary casing, including: a carrier section, a lateral section, and a main section. In use, the tool is run with the lateral section releasably held in coaxial alignment within the carrier section, and with the main casing section fixed to the lower end of the carrier section. Once in place in the enlarged section of the wellbore, the lateral section is released and diverted out of a preformed window in the lower end of the carrier section and runs generally parallel to the main casing section. In this manner a lateral junction is formed at the carrier casing window in which dual casing strings are connected to the primary casing. A second window, which is preformed in the upper end of the lateral section is aligned with the bore of the primary casing when the lateral casing section is fully extended out of the carrier section window, thus permitting recovery of a diverting device incorporated in the carrier casing section through the second window. The dual strings are then individually drilled and completed to target locations with pressure integrity between the dual strings maintained by using straddle equipment across the lateral junction.
U.S. Pat. No. 6,003,601, issued Dec. 21, 1999, to James R. Longbottom, discloses a method of completing a subterranean well and associated apparatus therefor provide efficient operation and convenience in completions where production of fluids occur from a lateral wellbore and a parent wellbore. In one disclosed embodiment, the invention provides a method whereby a tubular member may be extended from a parent wellbore into a lateral wellbore, without the need of deflecting the tubular member off of a whipstock or other inclined surface. The tubular member may be previously deformed and initially constraining within a housing, so that as the tubular member extends outwardly from the housing, the tubular member is permitted to deflect laterally toward the lateral wellbore.
U.S. Pat. No. 5,896,927, issued Apr. 27, 1999, to Roth et al., discloses methods of stabilizing the portion of an open-hole lateral well bore adjacent to and extending a distance from the junction of the lateral well bore with a primary well bore to prevent erosion and deformation of the lateral well bore during subsequent drilling and other operations. The methods basically comprise introducing a cement slurry into the portion of the lateral well bore adjacent to and extending a distance from the aforesaid junction under hydraulic pressure whereby the cement slurry enters voids and pore spaces in the walls of the well bore, allowing the cement slurry to set into a hard mass in the lateral well bore and then drilling excess set cement out of the lateral well bore. The stabilization ensures that when a liner is cemented in the lateral well bore, the junction between the liner and the casing in the primary well bore is sealed.
U.S. Pat. No. 5,730,221, issued Mar. 24, 1998, to Longbottom et al., discloses methods of completing a subterranean well provide access to a portion of a parent wellbore which has been closed off by a lateral wellbore liner. In a preferred embodiment, a method includes the steps of depositing cement in the lateral wellbore liner and then drilling through the cement and liner utilizing a bent motor housing conveyed on coiled tubing. The cement provides lateral support for a cutting tool while it is milling through the liner.
U.S. Pat. No. 5,803,176, issued Sep. 8, 1998, to Blizzard, Jr. et al., discloses a method for milling an opening in a tubular in a wellbore, the method comprising installing a mill guide in the tubular at a desired milling location, inserting milling apparatus through the tubular and through the mill guide so that the milling apparatus contacts the tubular at the desired milling location and contacts and is directed toward the tubular by the mill guide, and milling an opening in the tubular. In one aspect the method includes installing a whipstock in the tubular and disposing the mill guide adjacent the whipstock to protect a concave portion of the whipstock. In one aspect the method includes retrieving the mill guide from the wellbore and in another aspect includes retrieving the whipstock from the wellbore.
U.S. Pat. No. 5,862,862, issued Jan. 26, 1999, to Jamie B. Terrell, discloses an apparatus and associated methods of using provide access to a portion of a parent wellbore that has been separated from the remainder of the parent wellbore by a lateral wellbore liner. In a preferred embodiment, an apparatus has a cutting device, which may be a torch, a housing containing the cutting device, and an anchoring structure to fix the axial, radial, and rotational position of the apparatus relative to the liner. A firing head may be utilized to activate the cutting device.
Consequently, it is submitted that the prior cited hereinbefore, which does not include my recently filed prior patent applications, does not show a reliable technique for establishing a seal between a primary wellbore and one or more lateral wellbores. The prior art does not teach how to avoid contamination of the materials used to form a seal such as cement, epoxies, resins, or the like. The prior art does not disclose how to fill all the interstices between the casing in the primary wellbore and the liner in the lateral wellbore. Moreover, the prior art does not teach how to form a reliable seal with a reduced diameter under-reamer or hole opener. Therefore, what is needed is to somehow consistently and reliably provide a seal between a primary well and one or more lateral wells that will maintain a seal over a long period of time that may utilize a smaller diameter under-reamer. Those skilled in the art will appreciate the present invention which addresses these and other problems.
The present invention relates generally to an improved method of drilling multilateral wells. The method may comprise steps such as installing an arcuate guide, filling a portion of a primary wellbore with a stress resistant cement or epoxy resin, drilling an arcuate path through the hardened material to reestablish the primary well, and drilling a lateral well from the primary wellbore whereby the substance used in the primary wellbore seals and isolates the formation about the lateral wellbore while allowing a lateral well to be drilled that is substantially the size of the primary wellbore. More particularly, the substance used to fill the area about the junction resists cracks and fissures and retains a seal through the passage of time.
Thus, a method is provided for forming a sealed junction between a first wellbore and one or more lateral wells which branch from the first wellbore. The method may comprise one or more steps such as, for instance, enlarging a portion of the first wellbore to form an enlarged section of the first wellbore, installing an arcuate guide within the enlarged section, and then pumping material into the enlarged section. The material hardens within the enlarged section. Additional steps may include forming the one or more lateral wells by drilling out a lateral path through the hardened material whereby an interconnection of the first wellbore and the one or more lateral wells is formed within the hardened material.
In one embodiment of the invention, the material comprises an epoxy material.
Another step of the invention may include running the arcuate drillable guide into the first wellbore before the step of pumping. Additionally, the method may comprise reestablishing the first wellbore by utilizing the arcuate drillable guide for guiding a drill bit.
Preferably the method comprises positioning a deflection assembly within the arcuate primary well path. The deflection assembly may be created by mounting a whipstock to a sleeve within the primary well path.
In one presently preferred embodiment, the method includes positioning a packer within the enlarged section. Preferably the method then comprises inflating the packer during the step of pumping by pumping the material into the packer. In one embodiment, the method comprises positioning a packer around the drillable guide.
In other words, the method of the present invention may comprise filling a section of the first wellbore with a fluid material which hardens to form a solid material, and initiating drilling of the second wellbore from an arcuate section of the first wellbore to thereby form a junction of the first wellbore and the second wellbore within the solid material.
Thus, a downhole connection arrangement is created between a first wellbore and a second wellbore branching from the first wellbore. The connection arrangement may comprise elements such as an impermeable body formed of hardened material. The impermeable body may be positioned within the first wellbore. The body defines therein an arcuate first passageway. The arcuate first passageway may be an extension of the first wellbore. The body defines a second passageway therein. The second passageway may be an extension of the second wellbore. The first passageway and the second passageway interconnect within the hardened material of the body.
In one embodiment, the body is positioned within an enlarged portion of the first wellbore. In one presently preferred embodiment, the arrangement further comprises an inflatable packer with the body may be positioned within the inflatable packer.
A hollow orientation sleeve may be mounted within the body. Moreover, in one embodiment of the invention the impermeable body is substantially cylindrical.